1. Technical Field
The present invention relates to an inertial sensor.
2. Description of the Related Art
Recently, an inertial sensor has been used in various fields, for example, the military, such as an artificial satellite, a missile, an unmanned aircraft, or the like, vehicles, such as an air bag, electronic stability control (ESC), a black box for a vehicle, or the like, hand shaking prevention of a camcorder, motion sensing of a mobile phone or a game machine, navigation, or the like,
The inertial sensor generally adopts a configuration in which a mass body is bonded to a flexible substrate such as a membrane, or the like, so as to measure acceleration and angular velocity. Through the configuration, the inertial sensor may calculate the acceleration by measuring inertial force applied to the mass body and may calculate the angular velocity by measuring Coriolis force applied to the mass body.
A process of measuring the acceleration and the angular velocity by using the inertial sensor will be described in detail below. First, the acceleration may be obtained by Newton's law of motion “F=ma”, where “F” represents inertial force applied to the mass body, “m” represents a mass of the mass body, and “a” is acceleration to be measured. Therefore, the acceleration a may be obtained by measuring the inertial force F applied to the mass body and dividing the measured inertial force F by the mass m of the mass body that is a predetermined value. Meanwhile, the angular velocity may be obtained by Coriolis force “F=2 mΩ·v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity v of the mass body and the mass m of the mass body are values that are known in advance, the angular velocity Ω may be obtained by measuring the Coriolis force (F) applied to the mass body.
As described above, in order to measure the angular velocity Ω using the Coriolis force F, the mass body needs to be vibrated at a predetermined motion velocity v. However, when the mass body is vibrated, the inertial sensor according to the prior art may have a small amplitude and thus, sensitivity of a sensor may be degraded, due to damping force of air to a membrane. In addition, in order to implement the desired amplitude, the power consumption may be increased when the driving voltage is increased.
In order to solve the above problems, a technology of packaging the inertial sensor by depressurization or vacuum has been developed. However, in order to maintain the depressurization or the vacuum, a rigid encapsulation structure is needed and thus, manufacturing costs of the inertial sensor may be increased. In addition, since the complete sealing structure cannot be practically implemented, the sensitivity of the inertial sensor may be gradually degraded due to the introduction of air into the inertial sensor over time.